1. Field of the Invention
This invention relates to a device for controlling the position of a guide apparatus for rolling stock to be set at an entrance and other places of a rolling mill.
2. Description of the Prior Art
As described in Japanese Patent Application Disclosure No. SHO 61-241563(A) as one example, there has been so far known a positioning control device for a guide apparatus for rolling stock, which comprises a moving body for moving the guide apparatus, a feed screw shaft pierced through the lower portion of the moving body in the state engaged therewith, means for driving the feed screw shaft, and a fixing or locking means for securing the moving body.
The method of controlling the position of the guide apparatus for the rolling stock is fulfilled in the manner described below.
By operating the driving means to rotate the feed screw shaft, the moving body is moved along the roller shafts of pressure rollers in the rolling mill. The guide apparatus is controlled in position through the moving body so as to be moved to a prescribed position and secured by the fixing means at the prescribed position.
However, the conventional positioning control device involves the following problem to be solved.
Since the moving body is released from the fixing means while in movement consequently to form a gap between the contact surface thereof and the holding portion of the fixing means, there is a possibility of leaving the gap after positioning and securing the moving body and bringing the moving body out of position, as a result of which the moving body cannot be accurately positioned.
Furthermore, the moving body is prevented from moving in the axial direction of the feed screw shaft by the fixing means after being positioned, but it may possibly be displaced in the direction perpendicular to the axes of the pressure rollers, i.e. the forward and backward directions with respect to the rolling stock. As a result, accurate positioning control for the moving body cannot be fulfilled.
Also, there is a possibility of causing backlash between the male screw of the feed screw shaft and the female screw of the moving body. Accordingly, the conventional positioning control device has been required to be improved to achieve subtle accuracy in positioning the moving body.